576 The Architectural Review and American Builders' Journal. [Mar., ysing chemist of the party selling. No difference is carried to the umpire, un- less the two chemists vary two-tenths of a hundredth part. If they do, the chemical umpire makes his analysis of the contents of the sealed packet ; and the final analysis is equated between his result and that of the chemist for the purchaser, the process being long, but — for commercio-chemical analysis — very sure. No Cryolite can be shipped at Ivigtut, before its cubic contents have been taken by the Danish Comptroller, and he shall have given permission. After arriving at Philadelphia, the Cryolite is transported to Natrona, upon the Allegheny river, twenty-four miles above Pittsburgh, Pennsylvania, where a large and thriving village has sprung up, entirely owing to the exten- sive operations of the Pennsylvania Salt Manufacturing Compan}^ whose grounds here comprise some forty-five acres, twenty-five acres of which are actually covered by the buildings of the Company, forming one vast laboratory. From the time when all the soda of commerce was furnished by its simple collection JVom the lakes of Egypt, up through the period of its production by the burning of the sea-weeds of the coasts of Spain, Prance, Ireland and Scotland, there is no marked step, till the date of Le Blanc's invention of a method for its production from common salt. There are few chemical discoveries equal in importance to this. It has fostered the glass manufacturers' art, and the soap- makers' trade, and now gives employ- ment, in England alone to 90,000 people receiving annually over $4,000,000 in wages. It employs $10,000,000 of capi- tal, consuming annually 1,834,400 tons of raw material, producing 280,000 tons of finished products, with a value of $12,500,000. A step almost as great, as that made by Le Blanc, is the substitution, for his intricate and expensive methods, of the simple and comparatively cheap one of utilizing the native fluoride of alu- minium and sodium, or Cryolite, first proposed by Spilsbury as a source of soda. The comparison of the two methods may be thus made : — First. Le Blanc's method is compli- cated, requiring much costly " plant" or machinery, and giving rise, when exten- sively used, to immense quantities of hydro-chloric acid gas, as an incidental or waste product, requiring stringent enactments, with regard to its condensa- tion, for sanitary purposes. This h}'- dro-chloric or muriatic acid, the result of the action of oil of vitriol (Sulphuric acid) on common salt, for the production of Sulphate of Soda or " Salt Cake," con- stitutes the first stage in its manufacture. Second. The calcination of Salt Cake, with Limestone and Coal-dust, for the production of " Black Ball," or " Black Ash," an impure carbonate of Soda, mixed with Lime compounds. Third. The washing, or lixiviation, of the " Black Ash," for the separation of the soluble carbonate, and other soda salts, from the insoluble lime salts ; and the evaporation of this solution to dry ness. Fourth. The carbonating process : — that is, the conversion of any free or caustic soda — injurious to the glass manufacturer — into carbonate, which he requires. The supplementary stages consist of the production of various conditions of carbonate of soda, and of caustic soda, for their multifarious technical manipu- lations. The Cryolite process is as follows : — First. The calcination of the Cryolite with Lime, producing alumina, soda, and fluoride of calcium, or artificial Fluor-Spar. Second. The leaching, or lixiviation, of the calcined mass, for the separation of the insoluble fluoride of calcium from the soda, soluble itself, and dissolving also the alumina. Third. Passing carbonic acid gas (the
